1. Field of the Invention
The present invention relates to an electromagnetic clutch for a compressor, and more particularly, to a field coil assembly provided in an electromagnetic clutch for a compressor and a method for manufacturing the same.
2. Description of the Related Art
Generally, an electromagnetic clutch for a compressor is an electric device that forms a magnetic field by electromagnetic induction of a wound coil when power is supplied thereto. The magnetic force formed by the electromagnetic clutch causes a disc of a driving shaft of a compressor to be attracted toward a frictional surface of a pulley and dynamically connected thereto, so that the driving force of the pulley rotated by an engine is transferred to the disc of the driving shaft of the compressor. Accordingly, the electromagnetic clutch manages the power of the compressor according to whether the electric power is applied to the coil, thereby controlling the operation of a cooling system of an air conditioner.
FIG. 1 is a perspective view showing a conventional field coil assembly of an electromagnetic clutch for a compressor, and FIG. 2 is a plan view showing a major portion of a connector employed in the conventional electromagnetic clutch for a compressor.
As shown in the figures, a electromagnetic clutch for a compressor includes a pulley (not shown) connected to a crank shaft of an engine through a driving belt (not shown) and having a frictional side surface, a field coil assembly 1 housed in the pulley and supported by a housing (not shown) of the compressor to generate a magnetic flux by the applied power, and a disc and hub assembly (not shown) for transferring the power of the engine to the driving shaft of the compressor by bring a disc (not shown) into close contact with the frictional surface of the pulley using the magnetic flux generated by the field coil assembly 1.
A coil is provided in a body 2 that defines a framework of the field coil assembly 1, wherein the coil has a ring shape formed by winding a wire. A connector 10 is coupled to one side of the body 2. The connector 10 receives power and then transfers the power into the body 2 through terminals 15 so that the field coil assembly 1 forms a magnetic field.
An external appearance and framework of the connector 10 is defined by a housing 11. The housing 11 is made of an insulating material such as synthetic resin. A coupler 13 is formed at one side of the housing 11 such that it is coupled with a counterpart, and the terminals 15 are provided at one end of the coupler 13 to partially protrude therefrom.
At this time, as seen from FIG. 2, electronic elements such as a diode D and a resistance R are mounted in the housing 11. The diode D and the resistance R form a surge absorbing circuit in the connector 10 and are electrically connected to the terminals 15.
A manufacturing process of the connector 10 will be described. The terminals 15 are firstly insert injection molded to be integrated with the housing 11. In other words, the housing 11 is molded with the terminals 15 inserted in a mold assembly so that the terminals 15 are manufactured to be fixed in the housing 11.
In this state, the diode D and the resistance R are inserted into the housing 11. At this time, the diode D and the resistance R are assembled to be connected to ends of the terminals 15, and thermosetting resin such as epoxy-based resin E is injected into the housing 11 to fix the diode D and the resistance R.
Then, a wire W extending from the inside of the body 2 is connected to the connector 10. More specifically, in a state where one end of the wire W is inserted into a coupler 15′ formed at one end of the terminal 15, the coupler 15′ is tightened to fix the end of the wire W to the coupler 15′.
At this time, ends of the wire W, which extend from a coil (not shown) provided in the body 2, may be considered as parts of the coil.
A cover C may be provided in connecting portions between the wire W and the terminals 15. The cover C protects the connecting portions between the wire W and the terminals 15 from the outside and is configured as a separate part to thereby shield the connecting portions between the wire W and the terminals 15.
Accordingly, the terminals 15 are electrically connected to the ends of the wire W, so that the power transmitted through the connector 10 may be transferred to the coil through the ends of the wire W.
Recently, the present applicant has developed a technique to make the wire W of aluminum. In other words, the wire W may not be made of a copper material identical to the terminal 15 but an aluminum material that is lighter and relatively inexpensive.
However, the prior art discussed above has the following problems.
If the material of the wire W is different from that of the terminal 15, corrosion caused by contact between different kinds of metals, i.e., galvanic corrosion, may occur between the terminal 15 and the wire W. The galvanic corrosion is caused by a difference of potentials between two different kinds of metals exposed to the air, and the galvanic corrosion becomes more serious if the difference of potentials is greater or the metals are exposed to moisture.
At this time, copper and aluminum exhibits a great difference in their activations, and the field coil assembly is used in a vehicle where oxygen is easily supplied and temperature and humidity are relatively high. Thus, there is a problem in that galvanic corrosion may easily occur between the terminal 15 and the wire W.
In order to solve this problem, the connecting portions between the terminals 15 and the wire W may be shielded using a separate cover C as mentioned above. However, the cover C is a separate part, and moisture may penetrate through a gap between the cover C and the connector 10 to thereby cause corrosion between the terminal 15 and the wire W.
Also, this galvanic corrosion may result in electric short circuit between the terminal 15 and the wire W, which deteriorates reliability in operation of the electromagnetic clutch for a compressor.